1. Field of the Invention
This invention relates to illumination devices comprising light emitting diodes (LEDs) whose color temperature and/or brightness automatically changes throughout the daytime or nighttime and, when lighting changes are manually applied, the color temperature can advantageously change based on time of day.
2. Description of the Relevant Art
The following descriptions and examples are provided as background only and are intended to reveal information that is believed to be of possible relevance to the present invention. No admission is necessarily intended, or should be construed, that any of the following information constitutes prior art impacting the patentable character of the subject matter claimed herein.
Illumination devices, sometimes referred to as lighting fixtures, luminaires or lamps include incandescent illumination devices, fluorescent illumination devices and the increasingly popular light emitting diode (LED) illumination devices. LEDs provide a number of advantages over traditional illumination devices, such as incandescent and fluorescent lighting fixtures. Primarily, LED illumination devices have lower power consumption, longer lifetime, are constructed of minimal hazardous materials, and can be color tuned for different applications. For example, LED illumination devices provide an opportunity to adjust the chromaticity (e.g., from white, to blue, to green, etc.) or the color temperature (e.g., from “warm white” to “cool white”) to produce different lighting effects.
An illumination device can include a multi-color LED illumination device, which combine a number of differently colored emission LEDs into a single package. An example of a multi-color LED illumination device is one in which two or more different chromaticity of LEDs are combined within the same package to produce white or near-white light. There are many different types of white light illumination devices on the market, some of which combine red, green and blue (RGB) LEDs, red, green, blue and yellow (RGBY) LEDs, phosphor-converted white and red (WR) LEDs, RGBW LEDs, etc. By combining different chromaticity colors of LEDs within the same package, and driving the differently colored LEDs coated with or made of different semiconductor material, and with different drive currents, these illumination devices can mix their chromaticity output and thereby generate white or near-white light within a wide gamut of color temperatures or correlated color temperatures (CCTs) ranging from “warm white” (e.g., roughly 2600K-3700K), to “neutral white” (e.g., 3700K-5000K) to “cool white” (e.g., 5000K-8300K). Some multi-colored LED illumination devices also enable the brightness and/or color of the illumination to be changed to a particular set point. These tunable illumination devices should all produce the same color and color rendering index (CRI) when set to a particular brightness and chromaticity (or color set point) on a standardized chromaticity diagram.
A chromaticity diagram maps the gamut of colors the human eye can perceive in terms of chromaticity coordinates and spectral wavelengths. The spectral wavelengths of all saturated colors are distributed around the edge of an outlined space (called the “gamut” of human vision), which encompasses all of the hues perceived by the human eye. The curved edge of the gamut is called the spectral locus and corresponds to monochromatic light, with each point representing a pure hue of a single wavelength. The straight edge on the lower part of the gamut is called the line of purples. These colors, although they are on the border of the gamut, have no counterpart in monochromatic light. Less saturated colors appear in the interior of the figure, with white and near-white colors near the center.
In the 1931 CIE Chromaticity Diagram shown in FIG. 1, colors within the gamut 10 of human vision are mapped in terms of chromaticity coordinates (x, y). For example, a red (R) LED with a peak wavelength of 625 nm may have a chromaticity coordinate of (0.69, 0.31), a green (G) LED with a peak wavelength of 528 nm may have a chromaticity coordinate of (0.18, 0.73), and a blue (B) LED with a peak wavelength of 460 nm may have a chromaticity coordinate of (0.14, 0.04). The chromaticity coordinates (i.e., color points) that lie along the blackbody locus 12 obey Planck's equation, E(λ)=Aλ−5/(e(B/T)−1). Color points that lie on or near the blackbody locus provide a range of white or near-white light with color temperatures ranging between approximately 2500K and 10,000K. These color temperatures are typically achieved by mixing light from two or more differently colored LEDs. For example, light emitted from an RGB LEDs may be mixed to produce a substantially white light with a color temperature in the range of about 2500K to about 5000K. Although an illumination device is typically configured to produce a range of white or near-white color temperatures arranged along the blackbody curve (e.g., about 2500K to 5000K), some illumination devices may be configured to produce any color within the color gamut triangle formed by the individual LEDs (e.g., RGB).
At least part of the blackbody locus 12 is oftentimes referred to as the “daytime locus” corresponding to the Kelvin scale of color temperatures of daytime. For example, as shown in FIG. 2, several bounding boxes 14a, 14b, 14c and 14d are shown illustrative of color temperatures targeted to emulate daytime sunlight throughout the day. For example, 14a, 14b, 14c and 14d are chromaticity regions along the daytime locus of blackbody locus 12 (shown in dashed line) corresponding to target color temperatures in Kelvin of 6000K, 4000K, 3000K and 2300K, respectively. For example, the daytime locus color temperatures of 6000K can emulate blue sky noontime, 4000K can emulate a less blue mixture with some yellow overcast sky, 3000K can emulate a mixture of predominant yellow with some red morning sky, and 2300K can emulate predominant red with some yellow sunrise sky, similar to the differences between natural white, cool white and warm white color temperatures.
Some illumination devices allow color temperatures to be changed by altering the ratio of drive currents supplied to the individual LED chains. The drive currents, and specifically the ratio of drive currents, supplied to different colored LED chains can be changed by either adjusting the drive current levels (in current dimming) or the duty cycle (in PWM dimming) supplied to one or more of the emission LED chains. For example, an illumination device comprising RGB LED chains may be configured to produce a warm white color temperature by increasing the drive current supplied to the red LED chain and decreasing the drive currents supplied to the blue and/or green LED chain.
The color rendering index (CRI) is what defines the overall color or color appearance, and the CRI can be defined by the luminous flux (i.e., lumen output or brightness) and chromaticity. The brightness and chromaticity, or when mixed, the color temperature, can often form the target settings that change, due to changes in drive current, temperature and over time as the LEDs age. In some devices, the drive current supplied to one or more of the emission LEDs may be adjusted to change the brightness level and/or color temperature setting of the illumination device. For example, the drive currents supplied to all of the LED chains may be increased to increase the lumen or brightness output from the illumination device. In another example, as noted above, the color temperature setting of the illumination device may be changed by altering the ratio of drive currents supplied to the LED chains. As noted above, an illumination device comprising RGB LEDs may be configured to produce “warmer” white light by increasing the drive current supplied to the red LED chain and decreasing the drive currents supplied to the blue and/or green LED chain.
A need exists for an illumination device that can produce a different color or color appearance defined by brightness and chromaticity throughout the day, including evening and nighttime hours. It would be desirable to emulate a daytime locus, extending to nighttime, of one or more illumination devices configured in interior spaces of a structure. Periodic changes to the brightness as well as the chromaticity which forms the color temperature of one or more groups of illumination devices within one or more rooms is needed based on timing signals that are desirably sent periodically throughout the day. The desired timing signals can be sent from a timer remote from one or more groups of illumination devices in order to dynamically change the color temperatures so as to track, or correspond with, the emulated color temperatures external to the structure, and specific to outdoor sunlight or possible lack thereof.
There further remains a need for such an illumination system and method that need not rely upon sensor outputs in order to periodically change the color temperature output from a single illumination device or one or more groups of illumination devices. Dynamic changes in emulated color temperatures are selectively applied without use of sensor, but instead through use of time of day signals applied on a room-by-room basis. This proves advantageous and applicable to improved illumination systems that do not and cannot rely upon sensor outputs to periodically change color temperature output. Still further, it is desirable that whenever a task is needed that involves a change in color temperature output from one or more illumination devices, brightness can advantageously be changed manually to override the emulated sunlight, or lack thereof, output of color temperatures produced by the LEDs. Similar to the desired timer for producing times of day, output at regular periodic times, and corresponding color temperature changes in response to those times of day output, the desired illumination system can alter the dynamic and automatic emulated sunlight output by manually changing the brightness of all illumination devices within a group to produce differing changes in color temperature output depending upon the time of day in which the manual adjustment occurs. Advantageously, therefore, it is desirable to manually change the color temperatures relative to the time of day, and possibly more so during certain times of day than at other times. For example, when the emulated sunlight output mimics a higher color temperature near noon time, manual changes to brightness when tasking occurs will not substantially affect the high color temperature needed to maintain a more realistic noontime sunlight emulation. Yet, it is desirable to manually change the lower color temperature outputs during sunrise and sunset more so than at noontime, even though the brightness changes the same amount as noontime. It is therefore desirable to take advantage of the relationship between color temperature as a function of both the time of day and brightness so as to achieve task dimming (or reverse dimming) and resulting daytime emulation inside a structure that is more consistent with the actual sunlight occurring outside the structure. The emulation and manual override should be desirably applied to various groups of illumination devices within the structure. For example automatic emulation within a group of illumination devices within a bedroom should be different from that of a kitchen, and the manual override in each room should also be different due to different tasks needed to be performed in those rooms.